In the manufacturing process of wireless devices (e.g. cellular phones) that transmit and/or receive radio frequency (RF) signals, the wireless devices are tested at designated testing stations on the production line to ensure that the devices meet performance parameters regarding their transmit or receive functions. Conventional testing stations for wireless devices have fixtures configured to hold the device-under-test (DUT) in a specific position during testing, while probes make one or more conducted (wired) physical connection to the DUT. Passing devices are accepted and proceed to assembly and failing devices are rejected and repaired. Marginal units may be retested once or twice to confirm whether or not they pass. For maximum efficiency and profitability of the manufacturing process, the testing ideally consumes as little time as possible. This is especially important for original design manufacturers (ODMs) who rely on optimizing production times.
Reference wireless devices having known transmit or receive performance, commonly referred to as gold units (GUs), may be used to calibrate and verify the calibration of test stations. GUs may also be used to confirm test results for a DUT or deviations in DUT test results. For example, if two or more consecutive DUTs fail the test, the test can be run with a GU and the test results compared to diagnose a problem in the DUT production process, a defective component in the DUTs or inaccuracies in the test station. In order to verify the calibration of the test station with more granularity and to a desired level of thoroughness, it is useful to have a collection of GUs of varying standards such as “just good enough” GUs (i.e. units that should consistently pass the test at marginally acceptable limits) and “just bad enough” gold units (i.e. units that should consistently fail the test at marginally unacceptable limits).
The use of conventional test stations for wireless devices that require conducted connections to the DUT, and the associated use of GUs, possess several potential disadvantages. The need for physical connections between the test station and the DUT or GU typically requires the fixtures and probes of conventional testing stations to be specifically designed for, and therefore limited to use, with a particular DUT type (e.g. a specific make and model of cellular phone) or GU. Moreover, the DUT or GU may need to be precisely positioned within the test station by means of mechanical guides. Accordingly, a high level of effort, time and money is required to create DUT type-specific test stations and to reconfigure test stations for different DUT types. Among other things, new test fixtures and associated software may need to be installed in place of old test fixtures, tested, and calibrated. Testing rapidly becomes complex for MIMO DUTs having multiple inputs/multiple outputs. Physically connecting and disconnecting the DUT or the GU creates wear and tear on both the test station and the DUT or GU. Finally, it is difficult to create many GUs and maintain them to the level of desired performance. It is particularly difficult to create and maintain “just good enough” or “just bad enough” GUs to verify calibration at marginal pass or marginal fail limits, respectively.
Therefore, there is a need in the art for a system and method directed to calibration of test stations that mitigates the disadvantages of the prior art. Preferably the system and method will reduce the need for conducted physical connections between the test station and DUT and the need for dedicated GUs.